Using a Pruned Basis and a Sparse Collocation Grid With More Points Than Basis Functions To Do Efficient and Accurate MCTDH Calculations With General Potential Energy Surfaces
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Authors
Wodraszka, Robert
Carrington, Tucker Jr.
Date
2024-05-14
Type
journal article
Language
en
Keyword
Alternative Title
Abstract
We propose a new collocation multi-configuration time-dependent Hartree (MCTDH) method. It reduces point-set error by using more points than basis functions. Collocation makes it possible to use MCTDH with a general potential energy surface without computing any integrals. The collocation points are associated with a basis larger than the basis used to represent wavefunctions. Both bases are obtained from a direct product basis built from single-particle functions by imposing a pruning condition. The collocation points are those on a sparse grid. Heretofore, collocation MCTDH calculations with more points than basis functions have only been possible if both the collocation grid and the basis set are direct products. In this paper, we exploit a new pseudo-inverse to use both more points than basis functions and a pruned basis and grid. We demonstrate that, for a calculation of the lowest 50 vibrational states (energy levels and wavefunctions) of CH2NH, errors can be reduced by two orders of magnitude by increasing the number of points, without increasing the basis size. This is true also when unrefined time-independent points are used.
Description
This article may be downloaded for personal use only. Any other use requires prior permission of the author and AIP Publishing. This article appeared in Robert Wodraszka, Tucker Carrington; Using a pruned basis and a sparse collocation grid with more points than basis functions to do efficient and accurate MCTDH calculations with general potential energy surfaces. J. Chem. Phys. 7 June 2024; 160 (21): 214121. The publishers version and may be found at the journal website at https://doi.org/10.1063/5.0214557.
Citation
Robert Wodraszka, Tucker Carrington; Using a pruned basis and a sparse collocation grid with more points than basis functions to do efficient and accurate MCTDH calculations with general potential energy surfaces. J. Chem. Phys. 7 June 2024; 160 (21): 214121. https://doi.org/10.1063/5.0214557
Publisher
American Institute of Physics